FIG. 1 shows an conventional dental prosthesis for replacing a natural tooth. The dental prosthesis includes a dental implant that is implanted into a patient's bone. A dental abutment and screw are mounted on the dental implant. The abutment screw is torqued to approximately 35 N-cm. A crown can then be mounted on the abutment screw. FIG. 2 shows an exemplary dental implant 2 with an exemplary abutment screw 4 mounted in the implant. The screw 4 includes an abutment head 6, a neck 8, and a threaded portion 10 that is engaged with inner threads of the implant 2. Sometimes such an abutment screw can break at the neck 8 such that the abutment screw head 6 is removed but the threaded portion 10 and perhaps some of the neck remains stuck in the dental implant. This can happen, for example, due to excessive torque off axis or excessive forces on the mouth. Removing a remnant of a broken abutment screw from within a dental implant can be clinically challenging.
One removal technique is to drill a small hole within the broken fragment with reverse-oriented threads, then insert a smaller screw or tool into the reverse threads to unscrew the broken screw fragment. Another approach is to create a groove in the broken screw fragment to assist is turning it with a tool similar to a screw driver. However, these approaches can be problematic because they can further damage the broken screw fragment, can damage the internal dental implant threads, can cause the broken screw fragment to break up into smaller pieces, and/or can damage the surrounding dental implant. Another approach sometimes used is to manually attempt to turn the screw fragment with a dental explorer, however this technique can be time consuming and difficult to accomplish. Another approach is to use an ultrasonic instrument to pulsate the screw fragment and encourage rotational force.